Heterochrony of puberty in the European badger (Meles meles) can be explained by growth rate and group-size: Evidence for two endocrinological phenotypes

Effects of social environments on male primate HPG and HPA axis developmental programming

Developmental plasticity is particularly important for humans and other primates because of our extended period of growth and maturation, during which our phenotypes adaptively respond to environmental cues. The hypothalamus-pituitary-gonadal (HPG) and hypothalamus-pituitary-adrenal (HPA) axes are likely to be principal targets of developmental "programming" given their roles in coordinating fitness-relevant aspects of the phenotype, including sexual development, adult reproductive and social strategies, and internal responses to the external environment. In social animals, including humans, the social environment is believed to be an important source of cues to which these axes may adaptively respond. The effects of early social environments on the HPA axis have been widely studied in humans, and to some extent, in other primates, but there are still major gaps in knowledge specifically relating to males. There has also been relatively little research examining the role that social environments play in developmental programming of the HPG axis or the HPA/HPG interface, and what does exist disproportionately focuses on females. These topics are likely understudied in males in part due to the difficulty of identifying developmental milestones in males relative to females and the general quiescence of the HPG axis prior to maturation. However, there are clear indicators that early life social environments matter for both sexes. In this review, we examine what is known about the impact of social environments on HPG and HPA axis programming during male development in humans and nonhuman primates, including the role that epigenetic mechanisms may play in this programming. We conclude by highlighting important next steps in this research area.

Effects of weather and social factors on hormone levels in the European badger (Meles meles)

Animals in the wild continually experience changes in environmental and social conditions, which they respond to with behavioural, physiological and morphological adaptations related to individual phenotypic quality. During unfavourable environmental conditions, reproduction can be traded-off against self-maintenance, mediated through changes in reproductive hormone levels. Using the European badger (Meles meles) as a model species, we examine how testosterone in males and oestrogens in females respond to marked deviations in weather from the long-term mean (rainfall and temperature, where badger earthworm food supply is weather dependent), and to social factors (number of adult males and females per social group and total adults in the population), in relation to age, weight and head-body length. Across seasons, testosterone levels correlated postively with body weight and rainfall variability, whereas oestrone correlated positively with population density, but negatively with temperature variability. Restricting analyses to the mating season (spring), heavier males had higher testosterone levels and longer females had higher oestradiol levels. Spring oestrone levels were lower when temperatures were above normal. That we see these effects for this generally adaptive species with a broad bioclimatic niche serves to highlight that climatic effects (especially with the threat of anthropogenic climate change) on reproductive physiology warrant careful attention in a conservation context.

Assessing chronic stress in wild mammals using claw-derived cortisol: a validation using European badgers (Meles meles)

Measuring stress experienced by wild mammals is increasingly important in the context of human-induced rapid environmental change and initiatives to mitigate human-wildlife conflicts. Glucocorticoids (GC), such as cortisol, mediate responses by promoting physiological adjustments during environmental perturbations. Measuring cortisol is a popular technique; however, this often reveals only recent short-term stress such as that incurred by restraining the animal to sample blood, corrupting the veracity of this approach. Here we present a protocol using claw cortisol, compared with hair cortisol, as a long-term stress bio-indicator, which circumvents this constraint, where claw tissue archives the individual's GC concentration over preceding weeks. We then correlate our findings against detailed knowledge of European badger life history stressors. Based on a solid-phase extraction method, we assessed how claw cortisol concentrations related to season and badger sex, age and body-condition using a combination of generalized linear mixed models (GLMM) (n = 668 samples from 273 unique individuals) followed by finer scale mixed models for repeated measures (MMRM) (n = 152 re-captured individuals). Claw and hair cortisol assays achieved high accuracy, precision and repeatability, with similar sensitivity. The top GLMM model for claw cortisol included age, sex, season and the sex*season interaction. Overall, claw cortisol levels were significantly higher among males than females, but strongly influenced by season, where females had higher levels than males in autumn. The top fine scale MMRM model included sex, age and body condition, with claw cortisol significantly higher in males, older and thinner individuals. Hair cortisol was more variable than claw; nevertheless, there was a positive correlation after removing 34 outliers. We discuss strong support for these stress-related claw cortisol patterns from previous studies of badger biology. Given the potential of this technique, we conclude that it has broad application in conservation biology.

Early-life seasonal, weather and social effects on telomere length in a wild mammal

Early-life environmental conditions can provide a source of individual variation in life-history strategies and senescence patterns. Conditions experienced in early life can be quantified by measuring telomere length, which can act as a biomarker of survival probability in some species. Here, we investigate whether seasonal changes, weather conditions and group size are associated with early-life and/or early-adulthood telomere length in a wild population of European badgers (Meles meles). We found substantial intra-annual changes in telomere length during the first 3 years of life, where within-individual effects showed shorter telomere lengths in the winter following the first spring and a trend for longer telomere lengths in the second spring compared to the first winter. In terms of weather conditions, cubs born in warmer, wetter springs with low rainfall variability had longer early-life (3-12 months old) telomeres. Additionally, cubs born in groups with more cubs had marginally longer early-life telomeres, providing no evidence of resource constraint from cub competition. We also found that the positive association between early-life telomere length and cub survival probability remained when social and weather variables were included. Finally, after sexual maturity, in early adulthood (i.e., 12-36 months) we found no significant association between same-sex adult group size and telomere length (i.e., no effect of intrasexual competition). Overall, we show that controlling for seasonal effects, which are linked to food availability, is important in telomere length analyses, and that variation in telomere length in badgers reflects early-life conditions and also predicts first year cub survival.

Symbiotic microbiota and odor ensure mating in time for giant pandas

To achieve reproduction, male solitary mammals need to locate females using chemical communication with high levels of precision. In the case of giant pandas, the total estrus period of females was usually 15 days each year, however, successful mating activity is finished within 3 days from respective home range. The mating pattern of giant pandas, where multiple males compete for each female requires females employ efficient systems to communicate their estrus phases. To verifying whether the scent secretions of giant pandas changes by gender and estrus progression, the microbiota and compounds in 29 anogenital gland samples from 14 individuals during estrus were analyzed by 16S rRNA sequencing and GC-MS. We show that the microbiota communities covary by gender with 4 particular compounds of scent secretions. Among 597 genera, 34 were identified as biomarkers that could be used to distinguish between different estrus phases. By bacterial-compounds co-analysis, 3 fatty ester acids and squalene compounds covaried with the development of estrus in the bacterial communities of female giant pandas. This study helps clarify how a large, solitary mammal expresses accurate information to improve the likelihood of successful reproduction by changing the composition of microbiota and odor compounds of anogenital glands during estrus.

Infection with a Recently Discovered Gammaherpesvirus Variant in European Badgers, Meles meles, is Associated with Higher Relative Viral Loads in Blood

Herpesviruses are ubiquitous pathogens infecting most animals. Although host immunity continually coevolves to combat virulence, viral variants with enhanced transmissibility or virulence occasionally emerge, resulting in disease burdens in host populations. Mustelid gammaherpesvirus 1 (MusGHV-1) is the only herpesvirus species identified thus far in European badgers, Meles meles. No MusGHV-1 associated pathomorbidity has been reported, but reactivation of MusGHV-1 in genital tracts is linked to impaired female reproductive success. An analysis of a short sequence from the highly conserved DNA polymerase (DNApol) gene previously identified two variants in a single host population. Here we compared genetic variance in blood samples from 66 known individuals of this same free-ranging badger population using a partial sequence comprising 2874 nucleotides of the DNApol gene, among which we identified 15 nucleotide differences resulting in 5 amino acid differences. Prevalence was 86% (59/66) for the common and 17% (11/66) for the novel variant, with 6% (4/66) of badgers presenting with coinfection. MusGHV-1 variants were distributed unevenly across the population, with individuals infected with the novel genotype clustered in 3 of 25 contiguous social groups. Individuals infected with the novel variant had significantly higher MusGHV-1 viral loads in their blood (p = 0.002) after adjusting for age (juveniles > adults, p < 0.001) and season (summer > spring and autumn, p = 0.005; mixed-effect linear regression), likely indicating higher virulence of the novel variant. Further genome-wide analyses of MusGHV-1 host resistance genes and host phenotypic variations are required to clarify the drivers and sequelae of this new MusGHV-1 variant.

Variations in immune parameters with age in a wild rodent population and links with survival

Recent findings suggest that immune functions do not unidirectionally deteriorate with age but that a potentially adaptive remodeling, where functions of the immune system get downregulated while others get upregulated with age could also occur. Scarce in wild populations, longitudinal studies are yet necessary to properly understand the patterns and consequences of age variations of the immune system in the wild. Meanwhile, it is challenging to understand if the observed variations in immune parameters with age are due to changes at the within‐individual level or to selective (dis)appearance of individuals with peculiar immune phenotypes. Thanks to a long‐term and longitudinal monitoring of a wild Alpine marmot population, we aimed to understand within‐ and between‐individual variation in the immune phenotype with age, in order to improve our knowledge about the occurrence and the evolutionary consequences of such age variations in the wild. To do so, we recorded the age‐specific leukocyte concentration and leukocyte profile in repeatedly sampled dominant individuals. We then tested whether the potential changes with age were attributable to within‐individual variations and/or selective (dis)appearance. Finally, we investigated if the leukocyte concentration and profiles were correlated to the probability of death at a given age. The leukocyte concentration was stable with age, but the relative number of lymphocytes decreased, while the relative number of neutrophils increased, over the course of an individual's life. Moreover, between individuals of the same age, individuals with fewer lymphocytes but more neutrophils were more likely to die. Therefore, selective disappearance seems to play a role in the age variations of the immune parameters in this population. Further investigations linking age variations in immune phenotype to individual fitness are needed to understand whether remodeling of the immune system with age could or could not be adaptive.

Evidence for an adolescent sensitive period to family experiences influencing adult male testosterone production

SignificanceTestosterone influences how animals devote energy and time toward reproduction, including opposing demands of mating and competition versus parenting. Reflecting this, testosterone often declines in new fathers and lower testosterone is linked to greater caregiving. Given these roles, there is strong interest in factors that affect testosterone, including early-life experiences. In this multidecade study, Filipino sons whose fathers were present and involved with raising them when they were adolescents had lower testosterone when they later became fathers, compared to sons whose fathers were present but uninvolved or were not coresident. Sons' own parenting behaviors did not explain these patterns. These results connect key social experiences during adolescence to adult testosterone, and point to possible intergenerational effects of parenting style.

Adverse weather during in utero development is linked to higher rates of later-life herpesvirus reactivation in adult European badgers, Meles meles

Maternal immune and/or metabolic conditions relating to stress or nutritional status can affect in utero development among offspring with subsequent implications for later-life responses to infections. We used free-ranging European badgers as a host-pathogen model to investigate how prenatal weather conditions affect later-life herpesvirus genital tract reactivation. We applied a sliding window analysis of weather conditions to 164 samples collected in 2018 from 95 individuals born between 2005-2016. We test if the monthly mean and variation in rainfall and temperature experienced by their mother during the 12 months of delayed implantation and gestation prior to parturition subsequently affected individual herpes reactivation rates among these offspring. We identified four influential prenatal seasonal weather windows that corresponded with previously identified critical climatic conditions affecting badger survival, fecundity and body condition. These all occurred during the pre-implantation rather than the post-implantation period. We conclude that environmental cues during the in utero period of delayed implantation may result in changes that affect an individual's developmental programming against infection or viral reactivation later in life. This illustrates how prenatal adversity caused by environmental factors, such as climate change, can impact wildlife health and population dynamics-an interaction largely overlooked in wildlife management and conservation programmes.

Preserving identity in capture–mark–recapture studies: increasing the accuracy of minimum number alive (MNA) estimates by incorporating inter-census trapping efficiency variation

Quantifying abundance is often key to understanding ecological and evolutionary processes in wild populations. Despite shortcomings in producing accurate abundance estimates, minimum number alive (MNA) remains a widely used tool, due to its intuitive computation, reliable performance as an abundance indicator, and linkage to individual life-histories. Here, we propose a novel “efficiency-modified” MNA (eMNA) metric, which aims to preserve MNA’s favourable aspects while remedying its flaws, by incorporating (a) growth correlates to back-age individuals first captured as adults, and (b) estimates of undetected persistence beyond last capture based on time-varying capture efficiency. We evaluate eMNA through samplings of a simulated baseline population parameterised using data from a long-term demographic study of European badgers (Meles meles), under three different levels of capture efficiency (low; intermediate/“real” based on badger field data; high). We differentiate between eMNA’s performance as an abundance estimator—how well it approximates true abundance (accuracy)—and as an abundance indicator—how tightly it correlates with population abundance and changes thereof (precision). eMNA abundance estimates were negatively biased at all capture efficiencies. However, this bias was negligible at intermediate-to-high capture efficiency, particularly once low-information terminal sampling years (the first year and final three years of simulated studies) were removed. Excluding these years, eMNA under-estimated abundance by only 3.5 badgers (1.5% of population) at intermediate (real) capture efficiencies, and performed as a precise abundance indicator, with half the standard deviation of Cormack–Jolly–Seber probabilistic estimates and proving robust to inter-sampling variation in capture efficiency. Using undetected persistence probabilities to parameterise survival regression, we recreated baseline age-based survival relationships, albeit with some negative bias for under-represented ages. We offer considerations on the continued limitations of using eMNA for abundance estimates, minimum study duration for reliability, the metric’s benefits when individual identity is required, and potential for further improvement.

Alternative reproductive strategies provide a flexible mechanism for assuring mating success in the European badgers (Meles meles): An investigation from hormonal measures

Selection-pressures differ with population density, but few studies investigate how this can affect reproductive physiology. European badger (Meles meles) density varies from solitary to group-living across their range, with reported mating periods throughout the entire year to specific seasonal periods. Badger reproduction is evolutionarily distinct, interrupting the direct progression from conception to gestation with delayed implantation (DI), allowing for superfecundation (SF). To establish the tactical mating flexibility afforded by DI*SF, we used cross-sectional population-level seasonal variation of circulating sex-steroids for 97 females from a high-density population. Oestradiol was highest in spring among non-parous females, then lower in summer, and remained low during following seasons, suggesting that the mating period was restricted to just spring. Oestrone was consistently higher than oestradiol; it was elevated in spring, lowest during summer, peaked in autumn, and remained elevated for pregnant females in winter. This suggests that oestrone sustains pre-implanted blastocysts throughout DI. Progesterone was low throughout, except during winter pregnancy, associated with implantation and luteal development. In contrast to multiple mating periods reported by lower-density studies, our oestradiol data suggest that, at high-density, females exhibit only one mating period (congruent with testosterone patterns in males studied previously in this same population). While additional mating periods during DI enhance fertility assurance at low-density, at high-density, we propose that when coitus is frequent, fertilisation is assured, precluding the need for further cycles and associated mating risks. This endocrinologically flexible DI*SF mating strategy likely represents a form of balancing selection, allowing badgers to succeed at a range of regional densities.

Patterns of Genital Tract Mustelid Gammaherpesvirus 1 (Musghv-1) Reactivation Are Linked to Stressors in European Badgers (Meles Meles)

Gammaherpesvirus reactivation can promote diseases or impair reproduction. Understanding reactivation patterns and associated risks of different stressors is therefore important. Nevertheless, outside the laboratory or captive environment, studies on the effects of stress on gammaherpesvirus reactivation in wild mammals are lacking. Here we used Mustelid gammaherpesvirus 1 (MusGHV-1) infection in European badgers (Meles meles) as a host-pathogen wildlife model to study the effects of a variety of demographic, physiological and environmental stressors on virus shedding in the genital tract. We collected 251 genital swabs from 150 free-ranging individuals across three seasons and screened them for the presence of MusGHV-1 DNA using PCR targeting the DNA polymerase gene. We explored possible links between MusGHV-1 DNA presence and seven variables reflecting stressors, using logistic regression analysis. The results reveal different sets of risk factors between juveniles and adults, likely reflecting primary infection and reactivation. In adults, virus shedding was more likely in badgers in poorer body condition and younger than 5 years or older than 7; while in juveniles, virus shedding is more likely in females and individuals in better body condition. However, living in social groups with more cubs was a risk factor for all badgers. We discuss possible explanations for these risk factors and their links to stress in badgers.

Potentially toxic element accumulation in badgers (Meles meles): a compositional approach

Potentially Toxic Elements (PTEs) in Badgers (Meles meles), otherwise known as heavy metals, are unique amongst environmental pollutants occurring, both naturally and anthropogenically. PTEs have a broad range of negative health and environmental effects, therefore identifying their sources and pathways through the environment is imperative for public health policy. This is difficult in terrestrial systems due to the compositional nature of soil geochemistry. In this study, a compositional statistical approach was used to identify how PTEs accumulate in a terrestrial carnivorous mammal, Eurasian Badgers (Meles meles). Compositional principal component analysis (PCA) was used on geochemical data from the Tellus survey, the soil baseline and badger tissue data to map geo-spatial patterns of PTEs and show accumulative trends measured in time. Mapping PCs identified distinct regions of PTE presence in soil and PTE accumulation in badger tissues in Northern Ireland. PTEs were most elevated in liver, kidney and then muscle tissues. Liver and kidney showed the most distinct geo-spatial patterns of accumulation and muscle was the most depleted. PC1 and 2 for each type were modelled using generalised additive mixed models (GAMM) to identify trends through time. PC1 for the liver and muscle were associated with rainfall and ∂N15 in the liver, showing a link to diet and a bioaccumulation pathway, whilst PC2 for both tissues was associated with mean temperature, showing a link to seasonal activity and a bioaccessibility pathway. However, in kidney tissue these trends are reversed and PC1 was associated with bioaccessibility and PC2 with bioaccumulation. Combined these techniques can elucidate both geo-spatial trends in PTEs and the mechanisms by which they move in environment and in future may be an effective tool for assessing PTE bioavailability in environmental health surveys.

A non-invasive method to assess the reproductive status of the European badger (Meles meles) from urinary sex-steroid metabolites

Due to their unique reproductive physiology and behaviour, European badgers (Meles meles) are often used as a model to study mammalian reproduction. For reproductive endocrinology, circulating hormone levels are conventionally measured directly from blood samples. However, routine blood sampling is often not practical for wild animals and may induce stress affecting measurement accuracy. Non-invasive alternatives are thus of interest. Circulating hormones are metabolized through different routes, either by the kidneys, to be excreted through urine, or by the liver, to be excreted through faeces. These metabolites can thus be used as a proxy of hormone measurements, provided the species-specific metabolic characteristics are known. Here we tested the suitability of measuring urinary metabolites of circulating plasma sex-steroid hormones (testosterone in males and oestrogen in females) with enzyme immunoassays to assess the reproductive status of the European badger (Meles meles). Biological validation evidenced that urinary testosterone metabolite (UTM) and urinary total oestrogen metabolite (UEM) excretion patterns both corresponded with seasonal badger reproductive patterns on a population level, signaling correlation over a broad time frame. On an individual level, concurrent sampling of urine and plasma showed that male plasma testosterone and UTM levels correlated significantly across seasons, but no short term correlation was evident for total oestrogen and UEM in females. Thus, in badgers, urinary sex-steroid metabolites can be used reliably in the short term to assess male reproductive status at the individual level, but only at the broader population level for females.

Estimation of environmental, genetic and parental age at conception effects on telomere length in a wild mammal

Understanding individual variation in fitness-related traits requires separating the environmental and genetic determinants. Telomeres are protective caps at the ends of chromosomes that are thought to be a biomarker of senescence as their length predicts mortality risk and reflect the physiological consequences of environmental conditions. The relative contribution of genetic and environmental factors to individual variation in telomere length is, however, unclear, yet important for understanding its evolutionary dynamics. In particular, the evidence for transgenerational effects, in terms of parental age at conception, on telomere length is mixed. Here, we investigate the heritability of telomere length, using the 'animal model', and parental age at conception effects on offspring telomere length in a wild population of European badgers (Meles meles). Although we found no heritability of telomere length and low evolvability (<0.001), our power to detect heritability was low and a repeatability of 2% across individual lifetimes provides a low upper limit to ordinary narrow-sense heritability. However, year (32%) and cohort (3%) explained greater proportions of the phenotypic variance in telomere length, excluding qPCR plate and row variances. There was no support for cross-sectional or within-individual parental age at conception effects on offspring telomere length. Our results indicate a lack of transgenerational effects through parental age at conception and a low potential for evolutionary change in telomere length in this population. Instead, we provide evidence that individual variation in telomere length is largely driven by environmental variation in this wild mammal.

Effects of Mustelid gammaherpesvirus 1 (MusGHV-1) Reactivation in European Badger (Meles meles) Genital Tracts on Reproductive Fitness

Reactivation of latent Gammaherpesvirus in the genital tract can lead to reproductive failure in domestic animals. Nevertheless, this pathophysiology has not received formal study in wild mammals. High prevalence of Mustelid gammaherpesvirus 1 (MusGHV-1) DNA detected in the genital tracts of European badgers (Meles meles) implies that this common pathogen may be a sexual transmitted infection. Here we used PCR to test MusGHV-1 DNA prevalence in genital swabs collected from 144 wild badgers in Ireland (71 males, 73 females) to investigate impacts on male fertility indicators (sperm abundance and testes weight) and female fecundity (current reproductive output). MusGHV-1 reactivation had a negative effect on female reproduction, but not on male fertility; however males had a higher risk of MusGHV-1 reactivation than females, especially during the late-winter mating season, and genital MusGHV-1 reactivation differed between age classes, where 3–5 year old adults had significantly lower reactivation rates than younger or older ones. Negative results in foetal tissues from MusGHV-1 positive mothers indicated that cross-placental transmission was unlikely. This study has broader implications for how wide-spread gammaherpesvirus infections could affect reproductive performance in wild Carnivora species.

Social effects on age-related and sex-specific immune cell profiles in a wild mammal

Evidence for age-related changes in innate and adaptive immune responses is increasing in wild populations. Such changes have been linked to fitness, and knowledge of the factors driving immune response variation is important for understanding the evolution of immunity. Age-related changes in immune profiles may be owing to factors such as immune system development, sex-specific behaviour and responses to environmental conditions. Social environments may also contribute to variation in immunological responses, for example, through transmission of pathogens and stress arising from resource and mate competition. Yet, the impact of the social environment on age-related changes in immune cell profiles is currently understudied in the wild. Here, we tested the relationship between leukocyte cell composition (proportion of neutrophils and lymphocytes [innate and adaptive immunity, respectively] that were lymphocytes) and age, sex and group size in a wild population of European badgers (Meles meles). We found that the proportion of lymphocytes in early life was greater in males in smaller groups compared to larger groups, but with a faster age-related decline in smaller groups. By contrast, the proportion of lymphocytes in females was not significantly related to age or group size. Our results provide evidence of sex-specific age-related changes in immune cell profiles in a wild mammal, which are influenced by the social environment.

What lies beneath? Population dynamics conceal pace-of-life and sex ratio variation, with implications for resilience to environmental change

Life-history and pace-of-life syndrome theory predict that populations are comprised of individuals exhibiting different reproductive schedules and associated behavioural and physiological traits, optimized to prevailing social and environmental factors. Changing weather and social conditions provide in situ cues altering this life-history optimality; nevertheless, few studies have considered how tactical, sex-specific plasticity over an individual's lifespan varies in wild populations and influences population resilience. We examined the drivers of individual life-history schedules using 31 years of trapping data and 28 years of pedigree for the European badger (Meles meles L.), a long-lived, iteroparous, polygynandrous mammal that exhibits heterochrony in the timing of endocrinological puberty in male cubs. Our top model for the effects of environmental (social and weather) conditions during a badger's first year on pace-of-life explained <10% of variance in the ratio of fertility to age at first reproduction (F/α) and lifetime reproductive success. Conversely, sex ratio (SR) and sex-specific density explained 52.8% (males) and 91.0% (females) of variance in adult F/α ratios relative to the long-term population median F/α. Weather primarily affected the sexes at different life-history stages, with energy constraints limiting the onset of male reproduction but playing a large role in female strategic energy allocation, particularly in relation to ongoing mean temperature increases. Furthermore, the effects of social factors on age of first reproduction and year-to-year reproductive success covaried differently with sex, likely due to sex-specific responses to potential mate availability. For females, low same-sex densities favoured early primiparity; for males, instead, up to 10% of yearlings successfully mated at high same-sex densities. We observed substantial SR dynamism relating to differential mortality of life-history strategists within the population, and propose that shifting ratios of 'fast' and 'slow' life-history strategists contribute substantially to population dynamics and resilience to changing conditions.

Reproductive and Somatic Senescence in the European Badger (Meles meles): Evidence from Lifetime Sex-Steroid Profiles

Among the Carnivora, there is sparse evidence for any substantive fitness benefits of post reproductive lifespan (PRLS, survival after reproductive cessation, RC). Using the European badger (Meles meles) as a model species, we analyzed sex-specific cross-sectional endocrinological and morphological data to investigate: 1) age-dependent reproductive decline in sex-steroid levels versus prime reproductive age; 2) age-dependent declines in somatic condition and reproductive advertisement (from subcaudal scent gland secretion); 3) changes in reproductive success with age due to somatic and endocrinological decline; 4) occurrence of RC, PRLS, and post reproductive representation (PrR) in the population with reference to pre-pubescent hormone levels and evidenced by fewer cub assignments from pedigree. We provide strong evidence for a gradual, not abrupt, decline in sex-steroid levels with age, with both sexes following a concave (down) quadratic trend. For both sexes, the onset of decline in somatic condition commenced at the age of 3 years. In contrast, decline in reproductive hormones started at age ca. 5.5 years in females and 6 years in males, with similar rates of decline thereafter. Subcaudal gland secretion volume also decreased in both sexes, especially after age 5, suggesting less investment in reproductive advertisement. After age 3, fewer (surviving) females were assigned cubs. This coincided with the onset of somatic decline but came earlier than hormonal decline (5.5 years onwards). The decrease in offspring assignments commenced later in males at age 5-6 years; concomitant with onset of testosterone decline at 6 years. This suggests that, contrary to females, in males declining body condition does not preclude reproductive success (no 'restraint') in advance of hormonal senescence ('constraint'). There was evidence of female PRLS, with very old adults living up to 2.59 ± 1.29 years after RC; although in males this evidence was weaker. We discuss the implications of these findings for RC and PRLS in the context of adaptive and non-adaptive hypotheses. There was evidence of over 2 years of Post Reproductive Life Span in both sexes.

Knowing Me, Knowing You: Anal Gland Secretion of European Badgers (Meles meles) Codes for Individuality, Sex and Social Group Membership

European badgers, Meles meles, are group-living in the UK, and demarcate their ranges with shared latrines. As carnivores, badgers possess paired anal glands, but olfactory information on the content of badger anal gland secretion (AGS) is largely uninvestigated. Here, we examined the volatile organic compounds (VOCs) of AGS samples from 57 free-living badgers using solid-phase microextraction (SPME) and gas chromatography—mass spectrometry. AGS was rich in alkanes (C7–C15, 14.3% of identified compounds), aldehydes (C5–C14, 9.7%), phenols (C6–C15, 9.5%), alcohols (C5–C10, 7.3%), aromatic hydrocarbons (C6–C13, 6.8%), ketones (C6–C13, 6.3%) and carboxylic acids (C3–C12, 5.6%) and contained a variety of esters, sulfurous and nitrogenous compounds, and ethers. The number of VOCs per profile ranged from 20 to 111 (mean = 65.4; ± 22.7 SD), but no compound was unique for any of the biological categories. After normalization of the raw data using Probabilistic Quotient Normalization, we produced a resemblance matrix by calculating the Euclidian distances between all sample pairs. PERMANOVA revealed that AGS composition differs between social groups, and concentration and complexity in terms of number of measurable VOCs varies between seasons and years. AGS VOC profiles encode individual identity, sex and vary with female reproductive state, indicating an important function in intraspecific communication. Because AGS is excreted together with fecal deposits, we conclude that chemical complexity of AGS enables particularly latrine-using species, such as badgers, to advertise more complex individual-specific information than in feces alone.

Linkage between fecal androgen and glucocorticoid metabolites, spermaturia, body weight and onset of puberty in male African lions (Panthera leo)

There is limited physiological information on onset of puberty in male lions. The aim of this study was to use longitudinal non-invasive monitoring to: 1) assess changes in steroid metabolite excretory patterns as a function of age and body weight; 2) determine correlations between fecal androgen (FAM) and glucocorticoid (FGM) metabolite concentrations; and 3) confirm spermiogenesis non-invasively through urinalysis. Specifically, FAM and FGM metabolites were analyzed in samples collected twice weekly from 21 male lions at 17 institutions (0.9–16 years of age) for 3.8 months– 2.5 years to assess longitudinal hormone patterns. In addition, body weights were obtained approximately monthly from 10 individuals at five zoos (0.0–3.0 years), and urine was collected from six males at two facilities (1.2–6.3 years) and evaluated for the presence of spermatozoa. An increase in overall mean FAM occurred at 2.0 years of age, at which point concentrations remained similar throughout adulthood. The onset of puberty occurred earlier in captive-born males (<1.2 years of age) compared to wild-born counterparts (<2.5 years of age). Additionally, males in captivity gained an average of 7.3 kg/month compared to 3.9 kg/month for wild males over the first 2–2.5 years of age. Sperm (spermaturia) was observed in males as young as 1.2 years in captivity compared to 2.5 years in the wild (ejaculates). There was no difference in FAM or FGM concentrations with regards to age or season. Overall, this study demonstrates that: 1) captive male lions attain puberty at an earlier age than wild counterparts; 2) onset of puberty is influenced by body weight (growth rate); and 3) spermiogenesis can be confirmed via urinalysis. Knowledge about the linkage between body weight and onset of puberty could facilitate improved reproductive management of ex situ populations via mitigating the risk of unintended breedings in young animals.